JDM von Weinberg , Jul 10, 2012; 04:22 p.m.
Probably the best choice would be the newer Pentaxes, although I'll have to defer to the folks here on how easily the older manual M42 lenses work on these. I know there were M42>K adapters in the day when, but I haven't kept up with the Pentax lines.
For totally manual, stop-down metering and shooting, I will mention that M42 lenses work very well on Canon EOS digital SLRs (and film too) with an inexpensive adapter. For lenses that have the A-M switch this is easy, and for the others, some of the M42>EOS adapters have a flange that depresses the aperture pin.